This invention relates to a sliding door for vehicles, especially automobiles, which is guided longitudinally slidable by a single, horizontally oriented guide bar extending substantially over the door length in a guide head pivotally journalled about a vertical axis on a supporting arm itself pivotally mounted about a vertical axis on the vehicle body, and which, during opening, is initially displaceable into an intermediate position parallel to its closure position and subsequently displaceable longitudinally of the vehicle, whereby the outward pivoting motion of the sliding door into its parallel, intermediate position is regulated by a rod fitted pivotally about parallel axes firstly to the vehicle body and secondly to the guide head.
In a sliding door construction of the above type, as known from our own earlier proposal U.S. Pat. No. 3,650,338, the outward pivotal motion of the sliding door into its parallel intermediate position and its inward pivotal motion into its closed position are regulated by means of a rod hinged firstly to the vehicle body and secondly to the guide head in such a manner that the front edge of the sliding door, both upon entry into its closed position and also upon outward movement into the intermediate position, describes a fairly flat movement curve differing from a pure circular path. In order to achieve this, the supporting arm which receives the guide head and the rod associated with the regulating of the inward movement are of different lengths, and are moreover journalled at different spacings of their pivotal axes. To facilitate opening of the sliding door and to ensure that it is securely fixed in the final opened position, in this known construction, the use of a spring force is additionally necessary, which is provided by a tensile spring attached to the vehicle body and acting on the guide head. During the practical testing of sliding doors of the type of construction initially referred to, it has been found that it is desirable for the movement of the door body away from the seal surrounding the door opening to be as perpendicular as possible, during the outward movement of the door into its parallel intermediate position, both in view of the dynamic conditions and also in view of a reduced wear of the door seal.